The field of art to which this invention pertains is aryl cyanate esters, i.e., cyanic acid esters of polyhydric phenols.
Industry is constantly searching for lighter, stronger and more resistant materials to be used in place of the materials used today. For example, the aerospace industry is devoting considerable effort to utilizing structural composites in place of metals. Structural composites based on thermoplastic or thermoset resins and glass or carbon fibers have been and are being used successfully in many parts of military and commercial aircraft. Thermoset resins which are being used in such applications are epoxy resins, bismaleimide resins, and cyanate ester resins.
Cyanate ester resins, which are finding more and more uses, are based on the reaction products of polyhydric phenols and cyanogen halides. Such resins and their methods of preparation are described in U.S. Pat. Nos. 3,403,128 and 3,755,402. Additional patents which describe cyanate esters are U.S. Pat. Nos. 3,448,079, 3,987,230, 3,994,949, 4,022,755, and 4,330,658. Tris(cyanatophenyl)alkanes are described in U.S. Pat. No. 4,581,425. Even though these cyanate esters have exceptional properties when cured, there is a need for materials which have even better heat resistant properties and strength properties under adverse conditions.
Therefore, there is a continuing effort to find materials which have even higher heat resistance, moisture resistance, and strength properties.